Aug 8, 2013

Where to Learn Python ?

Starting to learn python and django in 2013 is great and here are some of my favourite links I like to give out when someone asks me.
 Here is a great online python terminal where you can try your python code out in the browser.
Some other great learn to program using python classes are here:

Finally but not least Geospatial Resources in Python

Happy programming

May 23, 2013

OGR2OGR examples for Spatialite, PostGIS, Shapefiles

I'm constantly trying to avoid Shapefiles but seem to only fail because some software GPS or GIS only supports Shapefiles as the interchange format.  Hence bye bye table names longer than 10 Characters (very annoying !) when going from a DB to Shapefile.

Here are some examples that I have recently used in doing some batch conversions here and there between PostGIS, Spatialite and Shapefiles.

My Setup:  Windows 7 Pro, 32 Bit,  ogr2ogr.exe  version GDAL 1.9.2, released 2012/10/08 (Installed using OSGeo4W  installer)

Example how to get version of ogr2ogr on my machine, at the command prompt.  Note your path to ogr2ogr is most likely not where I have it.

> c:/OSGeo4W/bin/ogr2ogr.exe/ogr2ogr.exe --version
  version GDAL 1.9.2, released 2012/10/08

So now the examples

Example 1.  upload all Spatialite tables to an existing PostGIS DB and existing tables with same name as the Spatialite table names

 c:/OSGeo4W/bin/ogr2ogr.exe/ogr2ogr.exe -append -lco GEOMETRY_NAME=geom -lco SCHEMA=geodata -f "PostgreSQL" PG:"host=localhost port=5432 user=username dbname=nameOfDatabase password=yourDbPassword" -a_srs "EPSG:31468" gisdata.sqlite

-append  appends data to existing tables
-lco GEOMETRY_NAME=geom   says the name of the geometry column should be "geom"
-lco SCHEMA=geodata     says the Postgis schema name is "geodata"
-f "PostgreSQL"    says destination is Postgresql Postgis format
PG:"...."   says connection information
-a_srs "EPSG:31468"   says the coordinate system is EPSG code 31468
gisdata.sqlite   this is the source Spatialite file with the tables to import into Postgis

if you just want to import the Spatialite tables into an existing PostGIS database and have the tables automagically auto created for you just ommit the -append   option above.

Example 2.  How to export all Spatialite tables into individual Shapefiles in an empty folder that exists.

c:/OSGeo4W/bin/ogr2ogr.exe -f "ESRI Shapefile" shp geodata.sqlite -dsco SPATIALITE=yes

shp      this is the name of the folder where the newly batch created shapefiles will go.
geodata.sqlite   this is the source Spatialite file with the tables to export to shapefiles
-dsco SPATIALITE=yes   says the input is in Spatialite format

in the end all the Spatialite tables will be exported to individual shapefiles (name = tableName) into the folder "shp"  the folder name can of course be whatever, where ever you want it on your machine. 

Example 3.  Convert a Spatialite file and all its tables into a new Sqlite table where the geometry is stored as Well Known Text

c:/OSGeo4W/bin/ogr2ogr.exe -f SQlite output.sqlite input_spatialdb.sqlite -dsco SPATIALITE=no -lco FORMAT=WKT

-f  SQlite    says the desitination format is SQlite
output.sqlite is the name of the newly created Sqlite database (must not exists before running)
input_spatialdb.sqlite    is the name of the Spatialite db with the source data
-dsco SPATIALITE=no   say destination output Sqlite is not Spatialite
-lco FORMAT=WKT    says output format of geometry columns data is Well Known Text format  (note: this could also be WKB for Well Known Binary)

So there you have it some conversion, batch and not so batch for you moving data between Spatialite, PostGIS and Shapefiles.

hope it helps you out.

Mar 14, 2013

Geospatial Web Visualisation

How do you visualize geo data on the web when you don't know which ones are out there?   This was the question I asked myself when thinking about how to explain this to my students. I then began to search and find out what is out there.

Geospatial Visualisation = Cartography  or ?   Well GIS has roots in computer visualisation and graphic design so where else but to start looking in these branches for new developments and here is what I found.

d3   Data driven documents. D3.js is a JavaScript library for manipulating documents based on data.
threejs threejs for 3d visualization in the browser   more cool 3d geospatial visualization on the web
dojo   Combine OpenLayers map data with additional features such as geo-referenced Dojo graphics shapes or geo-referenced Dojo widgets on top of the background map.
leaflet javascript api
openlayers javascript api
google maps javascript api
Google Charts Google charts can produce maps using google maps api
Modestmaps  modest Maps is a small, extensible, and free library for designers and developers who want to use interactive maps in their own projects
Kartograph   Kartograph is a simple and lightweight framework for building interactive map applications without Google Maps or any other mapping service.
gvisframework   GViz Framework is implemented using JavaScript to enable configurable integration of Visualization Components

this list is by no means complete and I welcome anyone to help fill this out.
Great links to more visualisation goodness: